The Munchkin is a relatively new breed of cat characterized by its very short legs, which are caused by a naturally occurring genetic mutation. Much controversy erupted over the breed when it was recognized by The International Cat Association in 1995 with critics voicing concern over potential health and mobility issues.

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Short-legged cats have been documented a number of times around the world since the 1940s. A British veterinary report in 1944 noted four generations of healthy short-legged cats which were similar to normal cats except for the length of the legs. This line disappeared during the Second World War but other short-legged cats were spotted in Russia during 1956 and the United States in the 1970s.[1]}

In 1983, Sandra Hochenedel, a music teacher in Louisiana, found two pregnant cats who had been chased by a bulldog under a truck. She kept one of the cats and named her Blackberry and half of her kittens were born short-legged. Hochenedel gave a short-legged male kitten from one of Blackberry's litters to a friend, Kay LaFrance, and she named the kitten Toulouse. It is from Blackberry and Toulouse that today's Munchkin breed is descended.[2]

Toulouse was an unneutered cat with outdoor access and after some time a population of stray short-legged cats started to form. Thinking that they might have a new breed, Hochenedel and LaFrance contacted Dr. Solveig Pflueger, a show judge, chairperson of The International Cat Association's (TICA) genetics committee and advisor to the Board of Directors. Together with Dr. David Biller, Head of Radiology at the College of Veterinary Medicine at Kansas State University, Pflueger conducted studies on the cats and determined that the short-legged trait has an autosomal dominant mode of inheritance and that the cats did not appear to have any spinal problems associated with those found in short-legged dog breeds such as the Corgi and Dachshund.[3]

The Munchkin cat was first introduced to the general public in 1991 via a national network televised cat show held by The International Cat Association (TICA) in Madison Square Garden.[3] Critics predicted that the breed would develop back, hip and leg problems similar to those that plague some Dachshunds.[4] Amidst much controversy, the Munchkin was proposed as a new breed by foundation breeders Laurie Bobskill and Robert Bobskill of Massachusetts and accepted by TICA into its New Breed development program in September 1994. One veteran show judge resigned in protest, calling the breed an affront to breeders with ethics.[2] The Munchkin achieved TICA Championship status in May 2003.[1]

Apart from TICA, registries that recognize the breed includes The American Association of Cat Enthusiasts (AACE), The United Feline Organization (UFO), the Southern Africa Cat Council,[5] and the Waratah National Cat Alliance in Australia.[6] There is controversy among breeders of pedigree cats as to what genetic mutations are abnormal and potentially disadvantageous to the cat.[7] Several cat registries do not recognize the Munchkin: Fédération Internationale Féline, which refuses to recognize what they consider a breed based on a "genetic disease", achondroplasia.[8] The Governing Council of the Cat Fancy likewise refuses to recognize the breed, considering this breed and others like it to be "unacceptable" because they are based on an "abnormal structure or development".[9] The breed is also not recognized by the Cat Fanciers' Association.[10] The Australian Capital Territory (a territory of Australia) government consider the munchkin breed to be "malformed animals" and the deliberate breeding of them "unacceptable" because of the "genetic health problems associated with such breeding".[11] Owners and Breeders of munchkins declare them to be "a sound breed" that is "ideal" for small homes and not particularly susceptible to health problems.[6]

The Munchkin is generally described as a sweet-natured, playful, people-oriented, outgoing and intelligent cat which responds well to being handled.[13] The shortness of their legs does not seem to interfere with their running and leaping abilities.[14]

The Munchkin has similar characteristics to normal domestic cats, due to their frequent use as outcrosses. It is a small to medium-sized cat with a moderate body type and medium-plush coat. Male Munchkins typically weigh between 6 and 9 pounds (3–4 kg) and are usually larger than female Munchkins, which typically weigh between 4 and 8 pounds. The hind legs can be slightly longer than the front which creates a slight rise from the shoulder to the rump. The legs of the Munchkin may be slightly bowed, although excessive bowing is a disqualification in the show ring. Cow-hocked legs are also penalized.[1][3]

The Munchkin comes in all coat colors and patterns. It also comes in a long-haired variety, which is shown in a separate Munchkin Longhair category. The short-haired variety has a medium-plush coat while the long-haired has a semi-long silky coat.[1] TICA rules for outcrossing allows the use of any domestic cat that does not already belong to a recognized breed. Similarity to other breeds is grounds for disqualification. Non-standard Munchkins are not allowed to be shown.[13]

Although the genetic mutation causing the short-legged trait in Munchkins has been referred to as achondroplasia,[8] achondroplasia is typically associated with an enlarged head as well as short legs. This combination of features is not seen in Munchkin cats. The condition has sometimes been referred to as hypochondroplasia or pseudoachondroplasia.[15][16] Small litter sizes when two munchkin cats are crossed indicate that embryos that are homozygous for the munchkin gene are non-viable.[16]

While there were early speculations that the Munchkin will develop spinal problems commonly seen in short-legged dog breeds, in 1995 several breeders had their oldest Munchkins X-rayed and examined for signs of joint or bone problems and found none.[17] However, there appears to be two conditions with increased incidence in the breed: lordosis (excessive curvature of the spine) and pectus excavatum (hollowed chest). Both conditions are commonly seen in humans with pseudoachondroplasia.[15] These conditions can appear in other breeds and some breeders have denied that it is a problem for the Munchkin.[3]

The munchkin gene is autosomaldominant.[8]Homozygous embryos for the munchkin gene are not viable due to gene lethality, and do not develop in the womb. Only kittens that are heterozygous for the munchkin gene develop into viable short legged munchkin kittens.[16] Because only heterozygous munchkin cats are able to pass on the gene, all litters with at least one munchkin parent have the possibility of containing kittens with the phenotypes: short-legged or normal-legged (referred to as non-standard munchkin), with the genotypes of Mm or mm, where M is the trait for short legs and m is the trait for long legs. The mating of two munchkin parents, Mm x Mm, have the chance of producing these offspring: 25% MM- a nonviable kitten, 50% Mm-short-legged, 25% mm- normal. The resulting litter will be 2/3 Mm-short-legged and 1/3 mm-normal.

Punnett squares, in which the M represents the dominant munchkin gene and the m represents the recessive normal gene, may be used to illustrate the chances of a particular mating resulting in a short-legged cat.

Kittens bearing two copies of the munchkin gene (MM) will not develop in the womb. Kittens bearing one munchkin gene and one normal gene (Mm) will be short-legged munchkins. Kittens bearing two normal genes (mm) will be normal. Mm munchkin kittens will be able to pass on the munchkin gene to their own offspring. Normal mm kittens will not, as they do not have a copy of the munchkin gene.

Mating two standard munchkins:

M

m

M

MM

Mm

m

Mm

mm

For each kitten conceived from this mating, there is a 25% chance it will fail to gestate, a 25% chance it will be normal, and a 50% chance it will be short-legged.

For each kitten conceived from this mating, there is a 0% chance it will be homozygous for the munchkin gene, a 50% chance it will be normal, and a 50% chance it will be a munchkin.

The Munchkin has been crossed with the curly-coated LaPerm to create the Skookum, the hairless Sphynx to create the Minskin and Bambino, with the extremely curly-coated Selkirk Rex to produce the Lambkin, the Persian breed group which includes Himalayans and Exotic Shorthair, to create the Napoleon and crossed with the Bengal to create the Genetta.

^ abWedderburn, Pete (October 2008). "Cat breeds–Trophies with hidden problems". Journal of Small Animal Practice. BSAVA Companion. 49 (10): 7–9. doi:10.1111/j.1748-5827.2008.00680.x. This selection for an albeit naturally occurring mutation, resulting in pseudoachondroplasia, has resulted in a breed which appears to have an increased incidence of pectus excavatum and spinal lordosis, both problems commonly seen in human patients with pseudoachondroplasia.